[TowerTalk] Coax loss. Has anybody measured it ?

[David Robbins]

This was used in a high voltage test lab where they were trying to measure
voltages from lightning and switching surges on 345kv or higher voltage
power lines.  I never saw that setup myself but the stories are that it was
the high resistance side of the voltage divider with a low resistance
termination as the other side.

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net


-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Don 
Sent: Sunday, November 30, 2014 03:58
To: Towertalk Reflector
Subject: Re: [TowerTalk] Coax loss. Has anybody measured it ?

Tektronix used nichrome coax for many of its passive probes, the almost
perfect lossy cable! Pretty small coax though!! I would believe other probe
mfrs used it too.

Don W7WLL

-----Original Message-----
From: Mike Fahmie via TowerTalk
Sent: Saturday, November 29, 2014 5:07 PM
To: Towertalk Reflector
Subject: Re: [TowerTalk] Coax loss. Has anybody measured it ?

How about maybe in a underground nuclear test bore hole, it would deliver
the signal before the coax melted entirely (?).-Mike-

      From: Jim Lux <jimlux at earthlink.net>
To: towertalk at contesting.com
Sent: Saturday, November 29, 2014 4:37 PM
Subject: Re: [TowerTalk] Coax loss. Has anybody measured it ?

On 11/29/14, 10:36 AM, David Robbins wrote:
> You want some lossy coax?  I have a couple old rolls where both the 
> center conductor and shield are nichrome.  VERY lossy stuff!
>
What would they use nichrome coax for? Some sort of test jig for heating?

For use in a refractory or corrosive environment? I think I've seen
hastelloy or something other superalloy.


I've seen stainless steel coax for cryogenic applications (very low thermal
conductivity going in and out of a dewar), but it had a thin silver plating.
For microwave frequencies, the plating was thicker than skin depth.

I've also seen delay line coax, where the center conductor is a tight
helix: the inductance/unit length is high so the propagation speed is slow
(and the Z is high, too). That stuff was quite lossy, although not in a
"dB/wavelength" sense.



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